French prosecutors have widened their investigation into corruption in athletics to include the bidding and voting processes for the hosting of the 2016 and 2020 Olympics.
Lamine Diack, the former president of world governing body the IAAF, is already being investigated by French authorities.
He was arrested last year on corruption and money laundering charges, over allegations he took payments for deferring sanctions against Russian drugs cheats.
Confirming the investigation was being widened, an official from the prosecutor's office said: "We are looking at these elements, but at this stage it is a question of verification. Nothing has been proved."
Tokyo, which will host the 2020 Olympics, defended the voting process when it came under scrutiny in January.
Rio 2016 organisers said on Tuesday that the city "won the right to host the Games because it had the best project".
"The difference in the votes, 66 to 32 against Madrid, excludes any possibility of an election that could have been rigged," communications director Mario Andrada said.
Diack, 82, was head of the International Association of Athletics Federations for 16 years until he stepped down last August.
He resigned as an honorary member of the IOC in November - a day after being provisionally suspended by the organisation following the start of the French investigation.
In December, a World Anti-Doping Agency (Wada) report into alleged IAAF corruption claimed Diack had been prepared to sell his vote to decide on the host city for the 2020 Games in exchange for sponsorship of IAAF events.
Diack's son Papa Massata, who was employed by his father as a marketing consultant for the IAAF, is also under investigation, and a warrant for his arrest has been issued by Interpol.
Last month, Wada investigators called for a follow-up inquiry into all World Championships awarded by the IAAF for 2009-2019 after finding evidence of possible wrongdoing.
Diack Jr has been banned for life by the IAAF but told the BBC in December he and his father were innocent of the claims against them.
Prosecutors are now looking into whether the alleged corruption could have extended to vote-rigging.
The Guardian claimed last year that - according to leaked emails - Diack Jr requested a payment of $5m from Doha in 2011, shortly before a decision was made about the city's unsuccessful bid for the 2017 World Championships. The Doha bid denies any wrongdoing.
In January, the newspaper reported he apparently arranged for "parcels" to be delivered to six IOC members in 2008, when Qatar was bidding for the 2016 Olympics, which will be hosted by Rio.
An IOC spokesman said the organisation had been in close contact with French prosecutors since the beginning of this investigation.
He added: "The IOC's chief ethics and compliance officer had already asked for the IOC to be fully informed in a timely manner of all issues that may refer to Olympic matters and has already applied to become a party to the investigations led by the French judicial authorities."